Dissolved gas analysis (DGA) in transformer oil is an important way to monitor the state of transformer equipment. CO, CH₄ and C₂H₂ are the representative dissolved gases in transformer oil. Based on the density functional theory, the optimal adsorption site of the transition metal atom Pt on the surface of WSe₂, one of the typical layered transition metal disulfides (LTMDs), is determined in the beginning. The adsorption behavior of these three gases on the surface of Pt-WSe₂is attained. The optimal structure of gas adsorption, charge transfer, adsorption energy, electronic density of states (DOS), deformation charge density (DCD), and frontier orbital are analyzed. As an electron acceptor, Pt-WSe₂ attracts electrons from all three gas molecules. The adsorption type of CO and C₂H₂ molecules is chemisorption, which means that the adsorption effect is strong. CH₄ adsorption is physical adsorption and the adsorption effect is weak. The adsorption of all the three gas molecules leads to an increase in the band gap of the Pt-WSe₂, resulting in the increase in the resistivity. The potential of applying Pt doped WSe₂ modified material to the detection of typical dissolved gas in transformer oil is explored and a theoretical basis is provided.